You might just be able to squeeze a very narrow stadium in there, if you knock down the club house and chop down a couple of trees. Most modern small stadiums seem to be about 120-140m wide, even wider if you consider the external concourses.
The entire east lower has sold out and they have sold about 300 tickets in the north stand, so I'd guess sales are at around 6000. Could be looking at around 6500 by Sunday, which will be a new club record.
We averaged nearly 3500 playing almost all our games at Crawley. Looks like we have already sold 6000+ for Spurs at the Amex on Sunday. I don't think averaging over 5000 at a permanent home in the city is particularly unrealistic and is a bit unambitious IMO.